U.S. Pat. No. 4,311,123 relates to a method and arrangement for controlling the fuel metered to an internal combustion engine. FIG. 2 of this patent shows the control of the fuel metered to the engine at the beginning and after the end of the overrun operation. When the accelerator pedal returns to its zero position, then the throttle flap reaches its idle position which signalizes the start of an overrun operation when the rotational speed is above a predetermined threshold value. A certain time duration follows during which the metering of fuel is maintained and the fuel metered to the engine is thereafter reduced according to a predetermined function whereafter fuel metered to the engine is abruptly interrupted. The overrun operation can be ended by a renewed desire on the part of the driver for acceleration or by a drop in engine speed into the range of idle speed. After the end of the overrun operation and independently of the manner in which the overrun operation is ended, a jump-like increase in the fuel metering to a value first takes place at which an ignitable mixture is provided for which the torque resulting therefrom is however not too great. This is advantageous when viewed in the context of a smooth transition between overrun operation and normal driving operation. The rate at which fuel is metered is then brought to a normal value pursuant to a selectable function after the jump-like increase in the metering fuel rate.
The known mixture control system has been found to be advantageous with respect to the driving performance obtained therewith. The additional function generator required for the known system has, however, been shown to be unsuitable with respect to the series manufacture of these systems.
U.S. Pat. No. 4,461,258 discloses a lambda control system wherein the individual proportional and integral components for the lambda control are stored and these components can be read out of the memory in dependence upon operating characteristic variables and serve for the lambda control. Such lambda control systems are at the present time used wherever the oxygen content in the exhaust gas is monitored when it is desired to have an exhaust gas with the least amount of contaminants and from there to lean the mixture or enrich the mixture with the aid of a two-point control process. An essential component of this system is a controller having at least an integrating capability.